This application claims priority of German Application No. 298 19 688.3 filed Oct. 29, 1998.
The invention relates to a lamphead, in particular a stage, film and/or television lamphead.
Lampheads of this nature generally have a one-sided or two-sided socketed lamp which is positioned in a case, for example a discharge lamp (e.g. a halogen metal vapour lamp or a natrium high pressure vapour lamp), whereby the lamp in association with a reflector which is also positioned in the case beams the light in one direction through an opening in the case. For the purpose of protecting the lamp and/or for the purpose of modulating the light beamed, the front side of the case is thereby closed with a cover component held in a frame or a holder, whereby this cover component is preferably transparent (e.g. a protective disc or a lens).
For the purpose of changing the lamp, the case must be opened. This frequently occurs through swivelling the cover component facing the case round a swivel axis which lies roughly tangentially on the edge of the case. DE 40 05 355 C2 disclosed, for example, a beaming light whereby the cover disc is secured by its frame to two mounting rods which are guided by means of a push-swivel-bearing on the case. For the purpose of changing the lamp, the cover disc is first pushed in the beam direction away from the case, and is then swivelled round a swivel axis positioned tangentially on the edge of the case.
Particularly with large, professional studio or stage lampheads, whereby the cover components can be larger than 400 mm, the existing opening mechanisms have the disadvantage that great forces and moments are at work through the large radial range of the cover component. This can lead to difficulties with changing the lamp, particularly when the lamphead in use is positioned in such a way that it can only be accessed with difficulty, e.g. on a crane, a stand, a telescope or under the cover. Through the high forces and moments which arise during opening, the entire lamphead is swivelled out of its adjusted position, which means that time-consuming further adjustment is then necessary.
It is thus an object of the present invention to provide a type of lamphead which for the purpose of changing a lamp can be opened on its front side simply and with little force application, and whereby upon opening the front side only limited forces and moments are at work.
A lamphead, in particular a stage, studio, film and/or television lamphead, is thereby provided which has a lamp positioned in a case, and whereby on the front side of the case there is a cover component which is in most cases more or less transparent and which is preferably equipped with a holder. This cover component closes the case in the beam direction of the lamp, and for the purpose of opening the case (e.g. for changing the lamp) the cover component can be swivelled facing the case. According to the invention, the swivel axis of the cover component thereby runs along a straight line which cuts the cover component in two points (secant) positioned at a distance apart from one another. This is unlike existing models whereby the swivel axis is generally positioned tangentially on the edge of the case or the cover component. The swivel axis preferably thereby runs near to the middle or even centrally or diametrically through the middle of the cover component.
According to the invention, the swivel axis of the cover component is moved away from the edge of the lamphead and/or the cover component and in the direction of the middle of the lamphead and/or the cover component. This can occur both with rounded and with angular, e.g. square lampheads and cover components, whereby in the case of angular cross-sections reference must correctly be made not to a xe2x80x9csecantxe2x80x9d, but instead for example to a straight line cutting the corresponding cross-section in two points.
The swivel axis is thus positioned in the area of the line bisecting the cover component, whereby the swivel direction of the cover component can be as one wishes. Preferably, however, the swivel axis will run vertically, in such a way that the cover component is swivelled horizontally. The area of the positioning of the swivel axis round the bisecting line includes the bisecting line. Preferably, however, the swivel axis will be positioned so far to the side of the bisecting line that when the cover component is opened this cover component with the smaller area is moved past, for example, a one-sided socketed lamp which is positioned in the middle of the lamphead reflector.
The solution according to the invention has the advantage that in the case of large and heavy cover components, like a lens (e.g. a Fresnel lens) or for example a plane disc serving as a protective disc, effect disc or filter disc, there is better weight distribution when the corresponding cover component is swivelled. As is otherwise generally the case, the cover component does not have to be swivelled far to the side, upwards or downwards, but instead is swivelled partially into the case, whereby particularly in the case of limited space availability this leads to simplified handling of the lamphead, e.g. when the lamp is changed.
In order to limit the opening angle, a catch is preferably provided. By swivelling the cover component, the case can thereby only be opened so wide as to ensure that the lamp cannot be damaged. The catch can, for example, be constituted by a securing pin or similar, or it can be already incorporated in the casting of the lamp case and/or the cover component or the frame thereof. It is also possible to have an adjustable catch, for variable adjustment of the maximum opening angle, e.g. by an adjustable securing bolt.
According to an embodiment of the invention, multiple cover components are combined together in a box, like for example a lens with a scattering disc and a dimming mechanism, whereby for the purpose of opening the case the complete box with all of the cover components can be swivelled round a swivel axis which runs along a secant of the cover components.
In a further embodiment of the invention, additional devices, e.g. separate color changers, dimming mechanisms or boxes with effect discs, filters and/or additional lenses, can be attached to the case and not to the swivelling cover component, nor to its swivelling holder or box. When the case is opened, the additional devices must not thereby be swivelled.